SUB-CLASS V 



GANOIDEI 



69 



Order 1. CROSSOPTERYGII, Huxley. Pringe-finned Ganoids. 



Notochord persistent or vertebrae ossified. Tau diphycercal or hetero-diphycercal, 

 Infraclavicle present. Paired fins with a scaly axis fringed on both sides by dermal 

 rays. Branchiostegal apparatus between the rami of the mandible consisting of a 

 pair of large jugular plafes, these in many Palaeozoic genera flanked by a series of 

 small lateral jugular s and an anterior median plate. Ganoid scales rhombic or 

 cydoidal, mmpletely covering the trunk and tail. 



Family 1. Holoptychiidae. Traquair. 

 Body covered with imhricating, cydoidal ganoid scales. No ossified vertebrae. 



Fio. 124. 

 Holoptychiios 7iobilisdmus, Ag. Upper 0kl Red Sandstone ; Scotland (restoration after Huxley 



Pectoral fins acutely lobate. Two dorsal fins and one anal fin, each borne by a 



distally expanded support (axonosf), followed by one or two rows 

 of short basal pieces (baseosts), which support the very numerous, 



Scale of Holoptychius 

 (Gly}}tolepis). Outer 

 (A), and inner (B) 

 aspect. Old Red Sand- 

 stoue ; Wik, Russia 

 (after Pander). 



Demlrodus Uporcatus, Ag. Tooth in side view (A), and from below (B), nat. size, 

 and transverse section of the same (C), highly niagnitted (after Pander). 



fine, dermal fin rays. Lateral jugular plates, clavicle, aiul infradavide present. 



